(1) Field
The present invention relates to a method and a device for acquiring and recording data captured in an aircraft. It relates in particular to the flight test installations for recording and viewing video, audio, graphical data and more generally any type of digital data.
(2) Description of the Related Art
It is known that the task of the flight test installations is to record the video sources, for example SDI (acronym for “Serial Digital Interface”, for serial digital interface), especially of test cameras or of videos originating from systems of the airplane, and certain data representing associated airplane parameters. The recording systems are proprietary systems which have necessitated adaptations to the needs of test airplanes. They store the data on magnetic tape cassettes. Depending on the year and on the technology then available on the market, different types of video recording format and of recorders have been used.
FIG. 1 schematically illustrates the functional blocks of a prior art video measuring system. In such a system, the need to time-stamp and associate data of airplane parameters with the video as well as the need to record as many channels as possible, has led to making adaptations to the professional hardware available on the market by avoiding certain functions as much as possible and by making qualitative and quantitative compromises.
As can be seen in FIG. 1, the video is obtained by camera transducers 105 and is then processed by processing means 115. A GMT 110 (acronym for “Greenwich mean time” for Greenwich mean time), or in other words a time stamp based on a universal time, is applied thereto in order to know precisely the progress of the test and to connect the video to all the other data obtained in parallel, especially the airplane parameters 120. For certain airplanes, the airplane parameters are calculated by an on-board calculator (not shown) and coded. The corresponding data are limited in number of parameters and in refresh speed. At the outlet of processing means 115, the signal is, for example, transported according to the SDI standard “SMPTE 259”. The speed of such a connection is fixed at 270 Mbps.
The signal is viewed on a view screen 125 during the test itself. It is noted that format converters (not shown) are necessary to view the SDI video signal. Furthermore, the video and the metadata, or in other words the parameters, identifiers of airplane, flight and hardware used, and the time, are recorded on cassettes 130 with a view to being analyzed, archived and/or stored by ground means 135. The recording format used is imposed by the recorder used. This format is intended for professionals only. Moreover, airplane data (type, No. etc.) are added to facilitate classification and archiving. These particulars are included on the cassette. In this way there is obtained a header for each cassette.
On the ground, the cassettes obtained are then analyzed by specialists on a processing bench. Magnetic tapes are processed in linear manner, the cassette having to be gone through to search for the desired sequence. In addition, since the airplane parameters are recorded in partial manner, a connection between the processing bench and a database is necessary.
As is understood upon reading the foregoing, the on-board architecture of the current video IEV (French acronym for “Flight Test Installation”) is therefore relatively complex by reason of the media used, or in other words magnetic tapes. The streams (video, audio and airplane parameters) are effectively recorded on cassettes.
This prior art has numerous disadvantages:                a video tape recorder makes it possible to record only video streams of standard definition, also known as “SD”. To be able to record video streams of high definition, also known as “HD”, it would be necessary to use video tape recorders of HDCam type, entailing extra cost. To be able to record graphical pages of ASVI type (acronym for “Avionics Serial Video Interface” for avionic serial video interface), relating to the cockpit instruments, or of VGA type (acronym for “Video Graphics Array” for graphic video matrix), it would be necessary to add modules for converting these signals to an SD or HD video signal;        the time-stamping of images on a video tape recorder takes place on the basis of what is known as a “timecode”, furnished by way of an AES signal (acronym for “Audio Engineering Society” for audio engineering society, a standardization organization that defines a digital signal structure for professional audio input). A hardware module making it possible to convert airplane time to AES timecode must therefore be developed specifically so that the images can be time-stamped on the basis of airplane time and        no system is provided with on a video tape recorder for recording dynamic parameters. A hardware module for encoding the airplane parameters on an audio track must therefore be developed to permit recording of these airplane parameters. Another hardware module must also be developed for reading of these parameters during processing on the ground.        the cassettes constitute a linear medium. This means that the different streams (audio, video and parameters) must be synchronized during acquisition. This poses a problem, because the times for transmission of these different streams are different.        